Process and apparatus for covering thin metal plates



' Nov. 9, 1965 J. DAUBERSY 3,216,106

PROCESS AND APPARATUS FOR COVERING THIN METAL PLATES Filed Feb. 23, 1962 INVENTOR Jed/7p fimzierzs y United States Patent 3,216,106 PROCESS AND APPARATUS FOR COVERING THIN METAL PL'ATES Jean Daubersy, Seraing, Belgium, assiguor to SA. Metallurgique dEsperance-Longdoz, Liege, Belgium Filed Feb. 23, 1962, Ser. No. 175,243 Claims priority, application Belgium, Feb. 24, 1961, 600,644 3 Claims. (Cl. 29-528) The present invention relates to a process and an apparatus for covering thin metal plates.

There are utilized in industry many covering surface treatments having a base of mineral and organic materials for the realization of which the plates are brought into contact with liquid products, reagents or varnish at surrounding temperatures or at least at temperatures not very high so that the plates brought to these temperatures can be oxidized by the air. In these processes the contact of the plate with the liquid can be eifected by soaking, by spraying or sprinkling or by passage between wet rolls.

It is thus that there is realized, for example, simple phosphatation, phosphatation by phosphatating varnishes, chromatation, and painting and covering by plastic materials. Furthermore there exist commercially a large number of reagents for surface treatment, and varnishes which can be applied to the plates by the same means and the composition of which is kept secret by the manufacturer. It is to this type of treatment and of a covering procedure that the invention relates, to the exclusion, for example, of coverings of molten metals which require appreciably higher temperatures.

In order to provide deposits on the surfaces of steel plates which are adhesive and capable in particular of insuring for the plates, an effective protection against corrosion, it is necessary that the deposits must meet special conditions, among which may be mentioned:

(1) The deposit must be made on a metallic surface which is clean and particularly one which is quite free from any trace of grease and carbon residues. In practice there are incorporated at the beginning of the lines serving for the covering of the plates, various degreasing devices, recourse being generally had in the last stage to electrolytic degreasing. This necessity for degreasing prior to the covering adds very appreciably to the cost of installations and the expenses of manufacture.

(2) There must not be in the deposit any discontinuity through which corrosion might start and penetrate gradually under the protective layer. Such defects in continuity, absolutely intolerable occur, for example, from the presence of small bubbles of air in the material deposited or from a lack of penetration of the deposit in certain imperfections of the surface of the metal plate such as traces of flaws, microfissures, granulation, scratches. Thus it is, for example, so diflicult to provide a continuous coating from plastic materials, that it is generally judged preferable in spite of the very high cost which results therefrom, to force adherence on the metal plate sheets of plastic perfectly free from defects in continuity obtained by calendering the plastic material.

(3) The deposit must Wet the plate and adhere thereto perfectly. In many cases this is not directly possible and there is used a deposit or intermediate treatment which improves the Wetting and/ or the adhesion. It may be mentioned, for example, the adhesive used for pasting the sheets of plastic as well as the phosphatation prior to painting.

3,216,106 Patented Nov. 9, 1965 The usual cycle of covering a metal plate comprises, starting with the cold rolling, in the following stages:

( 1) Cold rolling,

(2) Contingent degreasing of the coils and recoiling,

(3) Annealing the coils in a non-oxidizing atmosphere,

(4) Skin-pass by rolling,

(S) Degreasing, contingently electrolytic, and covering continuous or not according to the known processes such as aspersion, coating by cylinders, projection with the pneumatic pistol with or without electrolytic field, soaking and drying by cylinders.

The present invention afi'ords an economical solution to the ditficulties mentioned above due to a process of fabrication comprising an entirely new cycle.

The process, object of the present invention, is essentially characterized by a cycle of fabrication comprising the four following phases:

(1) A rolling of the metal plate in the cold state preferably without polishing the metal plate.

(2) Annealing of the metal plate as open coils in an atmosphere having a base of nitrogen, hydrogen and water vapor, comprising quantities of hydrogen and water vapor sufficient so that the surface of the metal plate will be absolutely free from any trace of grease and carbon as well as any oxidation.

(3) The removal of the open coil in the annealed state from the furnace, the conveying and the placing of this coil in a vat in which the covering operation is effected and this without the metal plate having been subjected to the operation of skinpassage and/ or any operation capable of fouling its surface.

(4) A skinpassage operation on the plate realized when the deposit has acquired a suflicient hardness.

The operation of depositing a protective coating on the metal plate may, according to an advantageous variant, be effected by placing the open coil in a vat in which a vacuum is created and into which there is then introduced, always under vacuum, the material which is to serve to constitute the protective coating.

According to another advanageous variant of the invention the material which is to serve to constitute the protective coating is first degasified, for example, under vacuum.

The present invention has likewise a further object to provide an apparatus for placing the process in operation.

The apparatus, object of the present invention, is essentially characterized in that it comprises in the following order: a cold roller, an apparatus for non-aging annealing of the open coils of sheet metal, a device for depositing on the coils an adhesive layer of a protective material, a reservoir and a circuit for supplying this material, and a skinpass roller.

The description given hereinafter by way of example will permit a better understanding of the invention and ofthe apparatus utilized.

The vat in which the covering operation is carried out and in which are deposited the coil or coils in open state must permit the application of vacuum. It comprises, therefore, a tight lid of a sufiicient diameter to permit the introduction of the open coil and is connected at the top to an apparatus for producing vacuum. The vacuum to be realized should not, furthermore, be very high, and it is limited to the industrial level of vacuum corresponding to placing in operation of a single machine or ejector, for example few millimeters of mercury. This degree of vacuum does not offer any difiiculties in the matter of tightness of the joints. At the bottom the vat is connected by one or more conduits to one or more reservoirs containing liquid materials, or those to be rendered liquid by heating, which will serve for treating or covering the metal plate. All these conduits are provided with stop cocks or regulating valves necessary for cutting off and regulating the vacuum, and to isolate the flow of these materials in one direction or the other.

The process of covering is carried out as follows.

The open coil or coils having been deposited in the vat, the lid is closed, the liquid reservoirs are isolated from the vat and a vacuum is produced in the latter. This operation removes the air from the surface of the metal plate and the small defects which are present therein are much more easily reached, and covered by the covering or treating liquids. One then proceeds to the introduction of the liquid material by opening the feed valve. The liquid enters the vat under the influence of the differences in pressure, the degree of vacuum being then regulated as a function of the volatility of the elements constituting these liquid materials. The liquid thus penetrates without interruption, the free space between the spirals and all the traces of air which might be present in the liquid and could cause the formation of small bubbles in the deposit are eliminated. For the materials particularly adapted to form such bubbles, for example the plastic materials, it is possible according to the invention to first degasify these materials in the storage reservoir wherein it suflices for this purpose to connect to the machine for producing vacuum, preferably at the time of filling. One then proceeds to the emptying of the vat by cutting off or diminishing the vacuum.

According to the invention this basic process can give rise to numerous modifications. Indeed it is clear to any technician that the conditions to be fulfilled for regulating the thickness of the deposits and to insure the setting or drying vary according to the nature of the liquid materials employed.

However the process of the invention is particularly flexible, and it is possible, for example, to complete the installation by devices for insufiiation of hot or cold air intended either to regulate the temperature of the coil or to accelerate the solidification of the deposits.

It is also possible to adjust the temperature, the fluidity of the materials used, the degree of vacuum and the speed of emptying the vat to regulate the thickness of the deposits.

It is likewise possible to provide for the introduction of the liquid materials in the vat by means of pumps when this introduction requires .adegree of vacuum incompatible with the volatility of the products.

It is also possible to provide the vat with an arrangement for condensing and recovering the vapors which escape during the filling, the emptying or the drying thereof.

It is also possible by the same method to treat the open coils in a series of vats containing different materials.

The process according to the invention is particularly adapted in the following cases of application:

(1) The application to metal plates of very thin coatings of an anti-corrosion covering intended to protect the plate during its stay in the shop and to facilitate the holding of the paint.

(2) The phosphatation prior to painting with or without a deposit of varnish.

(3) The deposit of plastic materials with or Without an intermediate layer of a phosphating deposit and/or an adhesive.

On the subject of the operation of the skin-pass which should be carried out after the deposits, it should be noted that:

(1) The percentages of elongation resulting are slight and generally can not destroy the covering. This elongation may be reduced when the annealing in open coil has been conducted so as to render the metal plate non-aging,

(2) In the case where the nature of the covering renders diificult the realization of a regular percentage of elongation it is possible to use skin-pass rolling mills regulating automatically the percentage of skin-pass.

(3) The surface of the cylinders utilized for the skinpass may be prepared so as to incrust covering designs of any type.

The following diagrammatic views of FIGURES 1 and 2 not according to scale and by way of non-restrictive examples will permit a better understanding of the invention, in which FIG. 1 represents a cycle of operation according to the invention and FIG. 2 representing a detail of FIG. 1.

The successive operations of the treatment is represented by the successive various parts 1 to 6 of FIG. I, the metal plate being moved in the direction of the arrows. The metal plate which is to be subjected to the treatment according to the invention, is cold rolled at 1 and immediately thereafter is placed in the form of an open coil at 2 and moved into a furnace 3 where it undergoes the annealing operation according to the invention. On leaving the furnace 3 the coil is subjected to the operation of a vacuum, represented diagrammatically at 4. After this the same coil is recoiled in nonopen form at 5 and the metal plate is subjected to a skinpass operation at 6.

The covering apparatus is shown in detail in FIG. 2. On leaving the furnace 3 the metal plate, in the form of an open coil 10, is introduced into the vat 13, the bottom of which is connected by a conduit to a reservoir 8 containing the material serving for covering the metal plate. At this instant the valve 9 is closed. The lid 11 is placed on the vat 13 in such a manner that the closure will be tight which is obtained by means of the joint 12. The vacuum is produced in the said vat by means of suction acting on the interior of this vat through a pipe line connected to the lid 11. The valve 7 places the interior of the vat in communication with the aspirating apparatus. Once the necessary vacuum is obtained the valve 9 is opened and the coveringv material contained in the reservoir 8 forced by suction into the vat 13 where it covers the coil 10. After this treatment the valve 7 is closed and the interior of the vat 13 is placed in communication with the outside air, the overflow of covering material returns to the reservoir 8, the valve 9 is closed and the coil 10 is withdrawn from the vat. The said coil is now ready for the following operation represented by the parts 5 and 6.

I claim as my invention:

1. A discontinuous process for covering thin metal plates with a protective non-metallic deposit comprising the successive steps of cold rolling the metal plate, annealing the metal plate in open coils in a furnace atmosphere with a base of nitrogen, hydrogen and water vapor comprising quantities of hydrogen and water vapors sufficient so that the surface of the metal plate will be absolutely free from any trace of grease and carbon and any oxidation, removing the open coil in the annealed state from the furnace and placing the coil in a vat wherein vacuum is created and then introducing into said vat under vacuum the material which is to serve to constitute the protective deposit, and a subjecting the coated plate to skin-pass operation when the deposit thereon has acquired a suflicient hardness.

2. A process according to claim 1, in which the material serving as the protective deposit is itself first degasified.

3. Apparatus for treating metal plates comprising a cold roller, a device for non-aging annealing the open coils of the metal plates, .a vat for receiving an annealed open coil, means for establishing vacuum in said vat, a reservoir containing a protective material, means supplying said protective material on said metal plates for depositing thereon an adhe sive layer of said material 2,797,476 7/57 Sendzir ir 117-11 9 XR and a skin-pass roller for said protective material on the 3,042,546 7/ 62 Hinningsen 1171 19 XR coated metal plates. OTHER REFERENCES References Cited by the Examiner 5 Vacuum Technique, Bushman, 1949, pp-

UNITED STATES PATENTS llggetals Handbook A.S.M., vol. I, 8th ed'., 1961, page 1,898,739 2/33 Me er 29-s27 XR 2,271,192 1/42 Hinz 117-119 XR WHITMORE A. WILTZ, Primary Examiner. 

1. A DISCONTINUOUS PROCESS FOR COVERING THIN METAL PLATES WITH A PROTECTIVE NON-METALLIC DEPOSIT COMPRISING THE SUCCESSIVE STEPS OF COLD ROLLING THE METAL PLATE, ANNEALING THE METAL PLATE IN OPEN COILS IN A FURNACE ATMOSPHERE WITH A BASE OF NITROGEN, HYDROGEN AND WATER VAPOR COMPRISING QUANTITIES OF HYDROGEN AND WATER VAPORS SUFFICIENT SO THAT THE SURFACE OF THE METAL PLATE WILL BE ABSOLUTELY FREE FROM ANY TRACE OF GREASE AND CARBON AND ANY OXIDATION, REMOVING THE OPEN COIL IN THE ANNEALED STATE FROM THE FURNACE AND PLACING THE COIL IN A VAT WHEREIN VACUUM IS CREATED AND THEN INTRODUCING INTO SAID VAT UNDER VACUUM THE MATERIAL WHICH IS TO SERVE TO CONSTITUTE THE PROTECTIVE DEPOSIT, AND A SUBJECTING THE COATED PLATE TO SKIN-PASS OPERATION WHEN THE DEPOSIT THEREON HAS ACQUIRED A SUFFICIENT HARDNESS. 